Nano - Silver Colorimetric Method Chiral Recognition Of Amino Acids

Chiral recognition is the important and special modes of molecular recognition. It is highly desirable to develop a simple, rapid, and high-throughput routine assay for chiral recognition. Colorimetric assay has attracted much attention because of its simplicity, fast, and practicality. Since color changes can be read out by the naked eye, colorimetric analysis does not require expensive or sophisticated instrumentation and can be applied to field analysis. In this thesis, we developed the AgNPs-based colorimetric approach for chiral recognition of amino acid.1. Colorimetric chiral discrimination of tryptophan and determination of enantiometric excess of tryptophan based on unmodified silver nanoparticlesTryptophan is an essential amino acid and the two enantiomers have different biological activities. In this work, a simple and rapid colorimetric method was developed for chiral recognition of D/L-Trp. It is based on the inherent chirality of AgNPs, and the unmodified AgNPs are used as chiral selector for D-and L-Tryptophan. In the presence of D-Trp, an appreciable yellow-to-red color of AgNPs solution can be observed, whereas no obvious color change is found in the presence of L-Trp. The chiral assay can be determined with the naked eye or using a UV-vis spectrometer. Furthermore, the chiral assay is used to visually determine the enantiometric excess of D-Trp. In this method, AgNPs do not need any labeling or modifying with chiral molecules. The method is more attractive because of its sensitivity, low cost, ready availability and simple manipulation.2.β-cyclodextrin-modified silver nanoparticles as colorimetric probes for direct visual enantioselective recognition of aromatic α-amino acidsβ-cyclodextrins (β-CDs) are promising and the most important macrocyclic hosts because they are water-soluble natural products, inexpensive, commercially available and readily modified. In this work, we propose β-cyclodextrin modified AgNPs as colorimetric probes for chiral recognition of aromatic amino acid. As reported in the literature, β-CDs showed different association constants with the isomers of aromatic compounds, In the presence of one enantiomer, the AgNPs solution showed a color change from yellow-to-red, whereas no color change was observed in the presence of the other enantiomer. The chiral assay also can be used to visually determine enantiometric excess. The method has such advantage as inexpensive, ready availability and simple manipulation.